[yaix]

Good point. But most of these apps are written, because they can make money for the author. There just isn't a large enough user base in Desktop Linux to make that money, and hence much less people willing to invest the time to write apps. And the much smaller userbase is split up between Gnome and KDE and now Unity and Xfce and so on. So there is even less incentive to write apps.

[tikhonj]

A program that works in KDE will work in Gnome and Unity and Xfce, so that divide is not strictly relevant. In KDE, at the very least, even GTk programs look very good. And, moreover, those programs would also work on Windows and OS X.